67 Double impact: hypophosphatemic rickets and vitamin D intoxication

Abstract Background Vitamin D prevents deficiency rickets, but its prescription must be weighed carefully! Objective We report a rare case of iatrogenic toxic hypervitaminosis D in a child with vitamin D resistant rickets…! Methods We admitted a two-year-old girl, presenting signs of rickets resistant to the usual then therapeutic doses of vitamin D3. Vitamin D2 in oral suspension is then ordered in addition, for a few weeks until the onset of hearing loss motivating her hospitalization in pediatrics. Results Biological and radiological explorations revealed renal failure with threatening arterial hypertension, as well as diffuse and severe arteriosclerosis on Doppler signal. Eviction (stopping vitamin D in all its forms), symptomatic and conservative management by (converting-enzyme inhibitors) and hydration allowed a progressive blood pressure normalisation, arteriosclerosis disappearance (undetected by Doppler signal and by angio-scan) along with a gradual normalising of the kidney function; all this over a period of 2 years The girl actually had hypophosphatemic rickets, and oral phosphorus (syrup) was also prescribed Conclusion Vitamin D is potentially toxic with sometimes severe renal risks (lithiasis, nephrocalcinosis), and hypercalcemia might be severe, especially if renal function is impaired. Blindly treating any rickets with vitamin D can be adventurous and might expose the child to serious morbidity.


Background
Vitamin D prevents deficiency rickets, but its prescription must be weighed carefully! Objective We report a rare case of iatrogenic toxic hypervitaminosis D in a child with vitamin D resistant rickets. . .! Methods We admitted a two-year-old girl, presenting signs of rickets resistant to the usual then therapeutic doses of vitamin D3. Vitamin D2 in oral suspension is then ordered in addition, for a few weeks until the onset of hearing loss motivating her hospitalization in pediatrics.

Results
Biological and radiological explorations revealed renal failure with threatening arterial hypertension, as well as diffuse and severe arteriosclerosis on Doppler signal. Eviction (stopping vitamin D in all its forms), symptomatic and conservative management by (converting-enzyme inhibitors) and hydration allowed a progressive blood pressure normalisation, arteriosclerosis disappearance (undetected by Doppler signal and by angio-scan) along with a gradual normalising of the kidney function; all this over a period of 2 years The girl actually had hypophosphatemic rickets, and oral phosphorus (syrup) was also prescribed Conclusion Vitamin D is potentially toxic with sometimes severe renal risks (lithiasis, nephrocalcinosis), and hypercalcemia might be severe, especially if renal function is impaired. Blindly treating any rickets with vitamin D can be adventurous and might expose the child to serious morbidity.

Case description
A 1 year 7-month-old African male presented with persistent fever, vomiting, diarrhoea and poor feeding for 6 days with irritability for 1 day prior to admission. The fever peaked at 40.2C. He had no cough, runny nose or difficulty in breathing. Five days prior to onset of the above symptoms, he was on outpatient treatment for acute tonsillitis and otitis media post exposure to SARS-CoV-2 from the older sibling. On examination he was noted to have oral thrush. 68  He was admitted to the general paediatric ward and was started intravenous fluids, azithromycin, ceftriaxone, paracetamol, ibuprofen and nystatin. Two days after admission, he was noted to be in fluid refractory shock, that needed inotropic support. He was transferred to Paediatric High Dependency Unit and received Intravenous fluids, oxygen via nasal prongs and transfused with packed red blood cells.
On day 3 of admission, he was noted to have red swollen cracked lips, exfoliation of skin, swollen feet with a vasculitic rash and a strawberry tongue. A diagnosis of Kawasaki disease with a differential of multisystem inflammatory syndrome was then made. Further investigations were done An ECHO was done that showed moderate cardiac dysfunction, with an Ejection Fraction of 51%, dilated chambers, and mild tricuspid and mitral valve regurgitation which was in support of MIS-C according to the CDC case definition. The child was started on IV immunoglobulin, and subsequent resolution of fevers and hypotension ensued. Three days later, he was noted to have recurrence of fevers and tachypnoea, with persistence of the swelling of the extremities. He received a 2 nd dose of IV immunoglobulin and aspirin. Antibiotics were changed to Meropenem, Vancomycin and Fluconazole. His respiratory status worsened, with increased oxygen demand. A chest X-Ray done showed features of pneumonia and a right sided pleural effusion. He was then transferred to ICU. A thoracocentesis was with drainage of 45mls of yellowish blood-stained fluid, with a mixed picture when subjected to Light's Criteria. At this point, the results from a COVID-19 IgG came back positive, clarifying the diagnosis to be MIS-C. Incidentally, was noted to have hypocalcaemia with low Vitamin D levels.
The patient improved with resolution of shock and the pleural effusions, and was discharged home after 13 days in hospital, on Aspirin, Prednisone, Omeprazole, Calcimax, Aldactone and Furosemide.
He was reviewed as an outpatient 12 days later, and he was clinically stable. A repeat ECHO was done which showed a structurally normal heart with an EF of 70%. He was advised to taper off steroids, stop furosemide and continue aspirin. A subsequent review 1 month later, showed that he was doing well. Aspirin was discontinued and he was discharged from the cardiac clinic. He was to be reviewed again in the rheumatology clinic after 4 months.

Discussion
Our patient's initial presentation was a confounder as it presented as acute gastroenteritis. His clinical picture evolved to present with features that fulfilled the criteria for Kawasaki disease and the case definitions for Multisystem Inflammatory Syndrome in Children (MIS-C) 1-3 . The initial presentation of gastrointestinal symptoms pointed towards a diagnosis of MIS-C, where gastrointestinal symptoms present in > 80% patients, with some presenting with acute surgical abdomen. His illness progressed rapidly to the point of requiring critical care due to haemodynamic instability, severe cardiac dysfunction and multi-organ involvement (renal, pulmonary, haematological